Terminal or pothead for electric cables



Jan. 8, 1935. F. c. MEYER ET AL 1,986,843

TERMINAL OR POTHEAD FOR ELECTRIC CABLES Filed Sept. l2, 1932 WINVENT()R. 2 8 BY w W MW wms.

Patented Jan. 8, 1935 UNITED STATES PATENT OFFICE TERMINAL R POTHEAD FORELECTRIC CABLES Application September 12, 1932, Serial No. 632,755

1 Claim.

This invention relates to a terminal or pothead construction forelectric cables and is more specifically directed to an improvedterminal or pothead construction for cables of the type in which theinsulated conductor is maintained at all times submerged in oil underhigh pressure as disclosed for example in Charles E. Bennett applicationSerial No. 563,714, filed July 29, 1931.

The drawing shows an embodiment of the invention in sectional elevation.Y

Referring to the drawing in detail, 1 designates the end of the sheathenclosing the cable, this sheath to be maintained filled with oil underpressure at all times. The sheath 1 is made up of an inner and outerlead sheath 2 and 3, respectively, and an intermediate layer or layersof canvas or other suitable fabric 4 provided for the purpose ofpermitting of expansion of the inner sheath 2 under the pressure of theoil and also for preventing bursting of the sheath. As will beunderstood this sheath construction is part of the cable system ratherthan a part of the terminal or pothead constituting the presentinvention.

Secured to the outside of this sheath construction is a sleeve or gland5 rigidly attached to the cable sheath by a wipe joint 6. The insulatedand shielded conductor of the cable passes out Y of the end of thesheath 1 and upwardly as 30 viewed in the drawing through the gland 5,the

metal shielding 7 terminating at 8 on the drawing. The gland 5 istapered on the inside as shown to gradually change the electrostaticstress from the conductor outward. The interior of the gland 5 ismaintained in communication with the interior of the sheath structure ofthe,

cable by slight mechanical clearance between the gland and the conductorof the cable. Pipe 9 is an oil supply line to take care of contractionand expansion of the oil due to thermal conditions.

Screwed into the upper end of the gland 5 is a pressure tube 10 ofinsulating material such as a phenolic condensation product, porcelainor other suitable material, having a specific inductive capacitydillerent from-that of the insulation of the conductor, the insulatedconductor extending upwardly through this tube and terminating adjacentthe upper end thereof as will be described presently. The pressure tubeclosely fits the insulation of the conductor so as to reduce as much aspossible the electrostatic stress on the oil in the tube.

Mounted on the upper end of the gland 5 is a metal shielding cone 11secured to the gland 5 by a wipe joint 12, the outward taper of thiscone being practically a continuation of the taper provided by taperingthe upper end of the gland 5 above referred to. The gland 5 is alsoprovided adjacent its upper end with an annular flange 13, and bolted tothis flange by bolts 14 is a metal cone 15 for supporting the terminalinsulator 16.

The upper end 1'7 of the insulated but unsheathed conductor of the cableis equipped with a connector 18 attached rigidly thereto in any suitablefashion, this connector 18 having a. stem 19 which extends to theoutside of the terminal through the top thereof.

The upper end of the pressure tube 10 is provided with a metal sleeve 20screwed in place thereon, the connector 18 just referred to passingthrough this sleeve. Bolted to the sleeve 20 by bolts 21 is a cap plateor ring 22 through which passes the stem 19 of the connector 18, the topof the connector being drawn up to this plate by a nut 23. Thisstructure seals the upper end of the pressure tube 10.

The metal cone 15 as above mentioned supports the insulator 16 of theterminal. The lower end of this porcelain is cemented as shown at 24 toa metal ring 25 secured to the cone 15 by the bolts 26. A washer 27insures a liquid-tight joint.

The upper end of the insulator 16 is provided with a cap plate 28 boltedto a ring 29 cemented or otherwise rigidly secured to the upper end ofthe insulator. This cap plate'is provided with a vent 30 for permittingof the escape of air from the interior of the terminal when the same isbeing filled with oil through the filler opening 31, this oil beingmaintained under gravity pressure as distinguished from the highpressures maintained on the oil in the cable pipe and within thepressure tube 10. A vent tube 32 is also provided in the cap plate 22 ofthe pressure tube for initially venting the tube.

The cone 6r grounding shield 11 supports a plurality of tubes 33 ofsuitable insulating material such as a phenolic condensation product,paper, etc. concentrically disposed with respect to each other and withrespect to the pressure tube 10 and its contained conductor. These tubesas will be seen from'the drawing are supported by the shielding cone 11.

It is to be understood that while the sheath of *the cable has beendescribedas composed of an inner and outer sheath with an intermediatefabric or other material for the purpose of this invention the sheathmay be of the fluted lead type.

It will be seen from all the foregoing that the pressure tube 10 is incommunication with the interior of the cable sheath 1 so that the highpressure maintained on the oil in the cable pipe or sheath is maintainedon the oil within the pressure tube while the oil of the terminalexterior of the pressure tube is only under gravity pressure, wherebythe advantages accruing to the use of oil under high pressure in directcontact with the exterior of the insulation of the cable are availableto the extreme outer end of the cable, without subjecting the porcelaininsulator 16 to any unusual pressure, this insulator being sealed offfrom the pressure tube and simply filled with oil under gravitypressure.

What is claimed is:

A terminal for high tension electric cables of the oil filled pressuretype wherein the insulated cable conductor is enclosed in a tubularcasing filled with oil maintained under high pressure, said terminalcomprising in combination a sleeve fitting over the end of the cablecasing and wiped thereto, said sleeve constituting a continuation of thecable casing to receive the insulated cable conductor, and flaringoutwardly on its interior adjacent the upper end of the sleeve graduallyto change the electrostatic stress from the conductor outwardly, apressure tube of insulating material for receiving the insulated cableconductor, said tube being screwed into the upper end of said sleeve toprovide a continuation thereof,

means for sealing the upper end of said pressure tube, a connectorsecured to the outer end of the conductor and projecting through theupper end of the pressure tube, a shielding cone surrounding the lowerend of the pressure tube and wiped to the outer end of said sleeve, theoutward taper of this cone being a substantial continuation of theoutwardly flaring interior of said sleeve, tubes of insulating materialsurrounding the pressure tube and concentrically disposed with respectthereto and with respect to each other, said tubes resting upon saidshielding cone to be supported thereby, said sleeve being provided withan annular flange, a conical metal member surrounding said shieldingcone and bolted to said annular flange, an insulator sealed to andsupported by said conical metal member and enclosing said shieldingcone, said tubes and said pressure tube, a plate for sealing the upperend of said insulator, a vent for said plate, a vent pipe for saidpressure tube extending through said plate, an insulating fluid undergravity pressure within said insulator and surrounding said pressuretube, said pressure tube and sleeve permanently separating the saidliquid insulation in the insulator from the; high pressure liquidinsulation in the pressure tube.

FRED c. MEYER. GEORGE E. om.

